Ammonia (NH3) is one of the most produced chemical compounds in the world. The global production reached 131M metric tons in 2010 (US Geological Survey 2012). Most of the produced ammonia is used in chemical fertilizers to provide the nitrogen crops need for growing. Ammonia has also been used to produce plastics, synthetic fibers and resins, explosives, and numerous other chemical compounds.
At present, ammonia production is resource intensive and produces unwanted greenhouse gases. The most common industrial method for producing ammonia is the Haber-Bosch process, where hydrogen gas derived from methane (from natural gas) and nitrogen gas react in the presence of iron or ruthenium catalyst to form ammonia (Smil 2001). According to the chemical fertilizer industry, each metric ton of ammonia produced by this process releases two metric tons of CO2, with an average recovery rate of some 38 percentage. Before being incorporated into a fertilizer product, the ammonia needs to be further reacted to produce known fertilizer compounds such as urea, ammonium nitrate, or ammonium phosphates. Nevertheless, despite the benefits of the Haber-Bosch process, there is a growing need to reduce the adverse environmental impact of fossil fuel based ammonia production and to find alternative methods for providing industrial quantifies of ammonia and ammonium for fertilizer and other industrial applications.
The biochemical process of converting nitrogen containing biological material into ammonia is called ammonification (Gowariker 2009) or mineralization. The scientific literature on bacterial ammonification is based on the spontaneous production of ammonia obtained from test tube scale laboratory studies and have been reported from at least 24 bacterial genera, mainly derived from the digestive tracts of ruminants (Bladen et al. 1961 and citations therein; Vince & Burridge 1980; Chen & Russel 1988; Russel et al. 1988; Attwood et al. 1998; Rychlik & Russel 2000; Eschenlauer et al. 2002; Whitehead & Cotta 2004) including gram positive and negative bacteria (Whitehead & Cotta 2004).
Of the bacteria capable of ammonification, i.e., producing detectable amounts of NH4+, only approximately 20 strains belonging to genera such as Clostridium, Eubacterium, Fusobacterium, Peptostreptococcus, and Pseudomonas, originally isolated from ruminal and swine manure, have been reported to form ammonia (NH3) at a rate of more than 40 nM (i.e., 681 mg NH3/liter=about 730 mg NH4+/liter) per 24 h (Paster et al. 1993; Attwood et al. 1998; Russel et al. 1988; Chen & Russell 1988; Whitehead & Cotta 2004). These bacteria have been described as hyper ammonia-producing (“HAP;” e.g. Attwood et al. 1998; Whitehead & Cotta 2004) and as hyper ammonia-producing bacteria (“HAB”) (Rychlik & Russel 2000).
The ammonia producing bacteria vary markedly in their preference of carbon source, as well as amino acids and peptides, of the substrate employed for ammonification (Vince & Burridge 1980; Rychlik & Russel 2000; Whitehead & Cotta 2004). The highest rate of production has been obtained in growth media containing peptides and amino acids digested from the milk protein casein (e.g., tryptone and casamino acids). With culture on intact casein, growth and production was detected from only 11 bacterial strains out of 40, including only a single strain with a high rate of production (47.6 mN NH3 per 24 hrs; Whitehead & Cotta 2004). Depending on the bacterial strain, the presence of glucose or lactose increased, had no effect on, or decreased ammonia production (Vince & Burridge 1980; Eschenlauer et al. 2002; Whitehead & Cotta 2004).
Thus, there remains a longstanding need for an improved process for producing ammonia from organic raw materials utilizing microbial culture.
The citation of any reference herein should not be construed as an admission that such reference is available as “Prior Art” to the instant patent application.